I agree with you that he can be both, but like @Timsup2nothin , I don't know about the dementia. However, I am certain he lies compulsively, about almost everything, all the time... and that he often tells lies about trivial things , lies when there is no real benefit to doing so, and tells lies that are demonstrably and obviously false. He also lies to paint himself in a more favorable light as both a victim and a hero, and he also tells lies that are fantastical and completely implausible.He can be both, you know.
I don't believe his total lack of concern for truth or facts is related to dementia. He has surely been that way his entire life. Dementia doesn't change who you are, not at first, but it does tend to magnify some pre-existing personality traits and reduce others, in part because it tends to reduce inhibition overall.
I think he is worse now, in terms of caring about the truth, being able to discern the truth, or in desiring to connect his opinions to facts. But yes, he has always been that way. I'm talking more about the fact that 30 years ago he came across like an educated adult, while now he comes across like a truculent fifth grader.
@El_Machinae - He will not plead the Fifth. His narcissism coupled with his compulsion for lying will not allow him to miss such a fantastic opportunity to spectacularly perjure himself on such a grand stage.